1. Field of the Invention
The present invention relates to a technology for managing a storage area in a storage system as disclosed in the specification of this application. More particularly, the invention relates to management of assigning a real storage area to a virtual storage area.
2. Description of the Related Art
In a computer system using a computer and a storage system, the amount of data stored in the storage system generally tends to increase. To cope with this increase, if a storage system having a sufficient data storage capacity is introduced from the beginning, a high introduction cost arises. On the other hand, if the data storage capacity of the storage system is expanded sequentially along with the increasing amount of data, a management cost for expansion arises. To reduce such introduction cost and management cost, a technology for the storage system to provide a virtual storage area to the computer was disclosed (e.g., refer to JP-A-2003-15915).
With this technology, the virtual storage area having sufficient data storage capacity is defined, but the physical storage area (e.g., storage area on a hard disk drive) is not assigned to all the virtual storage area. Thereafter, physical storage areas are sequentially assigned to the virtual storage area in accordance with a data write request into the virtual storage area. Since the physical storage area is not assigned to the unused range of the defined virtual storage area, the physical storage area can be effectively used.